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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.ipfilter;
17  
18  import io.netty.channel.Channel;
19  import io.netty.channel.ChannelFuture;
20  import io.netty.channel.ChannelFutureListener;
21  import io.netty.channel.ChannelHandler;
22  import io.netty.channel.ChannelHandlerContext;
23  import io.netty.util.internal.ConcurrentSet;
24  
25  import java.net.InetAddress;
26  import java.net.InetSocketAddress;
27  import java.util.Set;
28  
29  /**
30   * This class allows one to ensure that at all times for every IP address there is at most one
31   * {@link Channel} connected to the server.
32   */
33  @ChannelHandler.Sharable
34  public class UniqueIpFilter extends AbstractRemoteAddressFilter<InetSocketAddress> {
35  
36      private final Set<InetAddress> connected = new ConcurrentSet<InetAddress>();
37  
38      @Override
39      protected boolean accept(ChannelHandlerContext ctx, InetSocketAddress remoteAddress) throws Exception {
40          final InetAddress remoteIp = remoteAddress.getAddress();
41          if (connected.contains(remoteIp)) {
42              return false;
43          } else {
44              connected.add(remoteIp);
45              ctx.channel().closeFuture().addListener(new ChannelFutureListener() {
46                  @Override
47                  public void operationComplete(ChannelFuture future) throws Exception {
48                      connected.remove(remoteIp);
49                  }
50              });
51              return true;
52          }
53      }
54  }